This invention relates to an appendage correction device, in particular to an appendage correction device which is spring biased for correcting the attitude of a particular appendage of a human or mammal with respect to the particular portion of that human or mammal to which said appendage is attached. Examples include wrists, feet or other limbs, or one or more of a plurality of digits, or optionally the head of a human or mammal which are all prone to adopt incorrect or deficient attitudes.
A previous type of splint for extending a user""s fingers from a clawed position is shown in FIG. 1. This type of splint comprised a rigid back portion 10 to be secured to the back of a user""s hand and along their wrist. The back portion 10 is typically made of plastic and is preformed to follow the shape of a user""s hand and wrist.
One end of a spring 12 is secured at the end of the back portion 10 closest to the user""s elbow. The other end of the spring is secured to a piece of fishing line 14, which itself is secured to a sling 16 placed over the user""s finger. The fishing line 14 is run over a pulley 18 which is secured to a raised lip 20 at the end of the back portion 10 closest to the user""s fingers. The length of the spring 12 and fishing line 14 are arranged so that tension is exerted on the user""s finger to straighten the finger to improve the clawing condition. The splint is secured to the user""s wrist with straps 22. Typical examples of the splints described above can be seen in U.S. Pat. No. 4,949,711 (Gyovai et al.) and U.S. Pat. No. 4,765,320 (Lindemann et al.). An example of a foot splint working on similar principles is shown in U.S. Pat. No. 5,382,224 (Spangler).
The fundamental disadvantage with splints of the type described above arises from the simple physics associated with Hooke""s law for the extension of springs, being F=kx, where F is the force required to extend the spring, x is the extension of the spring under the said force, and k is the spring constant. When a user attempts to grip an item by curling his fingers, he has to apply a muscular force to overcome the resistance of the spring before his fingers will curl. In accordance with Hooke""s law, this force increases as the spring extends and thus renders the gripping and manipulation of items difficult, especially small items where one or more of the fingers of the user may be required to be curled through 90xc2x0 such that the fingers are perpendicular to the palm of the had or through a even greater angle.
Also, the grip cannot be maintained for any great length of time because a continuous force must be used to maintain the extension of the spring. Typically, such a device becomes painful to wear after one or two hours.
A further disadvantage of the existing splints is the gradual deterioration of their therapeutic effect as the fingers are straightened. It is most preferable for splints to exert only a nominal correcting force on the fingers at first to avoid inflicting excessive pain and discomfort caused by immediately applying a large correcting force, and thereafter steadily increase the correcting force. However, existing splints function in the entirely opposite manner as they are usually first applied when the fingers are completely clawed, and the springs which apply the correcting force to the fingers are therefore at their maximum extension. Henceforth as the fingers are straightened, the spring extension reduces as does the correcting force, hence necessitating the use of a number of different springs of different lengths or spring constants which can be successively affixed to the splint and to the finger slings after the attitude of the fingers have been corrected by an appropriate amount. Only in this manner can a suitable correcting force be continually applied to the fingers.
It is commonly believed that utilisation of the deficient limbs or digits during the period of correction is therapeutic and can reduce the time taken to effect the correction. Existing splints do not offer the facility for utilising the fingers because the wearer is dissuaded from so utilising his fingers on account of the increased force required to move same, and concomitantly the increased pain and discomfort which may be associated with such movement.
It can be appreciated from the above that existing splints are cumbersome and unwieldy, and require the continual changing of springs as the deficiency of the user is corrected. This means that the user is required to return to hospital periodically which is undesirable. Ultimately, existing splints are so troublesome to users that they are often completely removed and discarded by the user who would rather suffer the problems associated with a clawed hand than continually wear the splint. Such circumstances are completely unacceptable, and the present invention has as one of its objects the mitigation of the above disadvantages.
Furthermore, this previous type of device does not allow a user to move his wrist.
According to the invention there is provided a correction device for correcting the attitude of one or more digits of a hand from a curled position into a straight condition in which said digits extend away from the palm of said hand, said device comprising a base portion having means for securing the device to the hand behind the digits, said base portion having a front edge proximate the digits and a rear edge disposed at least partially around the hand behind the digits, a projection member pivotally attached to the base portion proximate the front edge of the base portion and having a longitudinal axis, a free end and a pivoting end, a flexible sling depending from the free end of said projection member and adapted to support a digit therein, a resilient member having a longitudinal axis and being secured at a first end to said projection member at a position remote from the pivoting end of said projection member and at a second end to said base portion, the free end of said projection member being rotateable both towards and away from the rear edge of said base portion, rotation away from sad rear edge causing elastic extension of the resilient member which exerts a force on said projection member which both resists said rotation and gives rise to a couple about the pivotal attachment of said projection member which progressively decreases in magnitude as said free end of said projection member rotates away from the rear edge of said base portion and the digits supported by the sling means connected to said projection member adopt positions with greater degrees of curl, said resilient member being attached to said base portion rearwardly of the pivotal attachment of said projection member to said base portion, wherein the point of attachment of said resilient member to said base portion, the pivotal attachment of said projection member to said base portion, and the point of attachment of said resilient member to said projection member are substantially aligned when the sling means supports digits which assume the curled posit ion thus substantially eliminating the couple acting on the projection member to rotate same back towards the rear edge of said base portion.
Preferably the resilient member is linear, and the rotation of the projection member simultaneously reduces the angle subtended between said resilient member and said projection member such that the magnitude of the component of the restoring force carried by the projection member increases, whereas the magnitude of the component of the restoring force transmitted to the appendage decreases.
Preferably, for example where the device is a dynamic finger splint, the base portion is secured to the portion of the user to which the appendage is attached, and the projection member is provided with means to transfer a component of the correcting force between the base portion and the projection member exerted by the resilient member to the fingers, such as a finger sling.
The device may be a finger splint. A sling portion may be secured to the protection member. The sling portion may be finger sling. The splint may comprise a plurality of sling portions and/or resilient members.
In the second position the projection member may be beyond, preferably just beyond, alignment with the longitudinal axis of the base portion. Preferably the projection member is movable through an angle greater than 90xc2x0.
The first end of the resilient member may comprise an attachment section, which may be arranged to communicate with a corresponding attachment section of the base portion. The attachment sections may be communicating pegs and openings, or alternatively Velcro(copyright) may be used to secure the resilient member to the base portion.
The base portion may comprise a plurality of said openings, arranged longitudinally along the base portion. The resilient member may be a coiled spring.
The projection member may comprise an extension section, which may extend from a free end thereof. Preferably, the extension section extends away from the resilient member.
The sling portion may be attached to the extension section, preferably by a string or wire. The sling portion may be secured substantially perpendicularly to the extension section, to thereby reduce lateral forces between the sling portion and the user""s appendage.
The base portion may be secured to the hand with straps, which may have hook and pile fastener secured thereto.
The device according to the invention has a number of advantages over currently existing splints, and these are now explained.
The component of the correcting force applied between the appendage and the portion of the user to which said appendage is attached progressively reduces and is increasingly carried by the projection member of the device as it rotates about the base portion. This is invaluable because firstly, the component of the correcting force applied to the appendage progressively increases as the projection member rotates in a direction which reduces the extension of the resilient member because as it does so, the angle between the projection member and the resilient member increases and accordingly the component of the correcting force carried by the said projection member decreases. This is desirable from a medical perspective as discussed above.
Secondly, when the projection member has rotated to such an extent that it is substantially parallel with the resilient member, almost the entire correcting force applied by the resilient member between the projection member and the base portion is carried by the projection member. The component of the Correcting force transmitted to the appendage is minimised, and in the case of a finger splint, the user can grasp and manipulate items with relative ease. Indeed, the user can be quite dextrous when the projection member is in such an orientation.
A further advantage of the device is that even when the projection member is substantially parallel with the resilient member, a slight residual force is transmitted to the appendage digit, both as a result of the bending of the resilient member over the attachment of projection member to the base, and also because the resilient member is never completely parallel with the projection member and thus a small component of the force of the spring is always transmitted to the appendage This ensures the continual efficacy of the device because unless the user is attempting to move the appendage against the action of the resilient member and so reduce the correcting force applied thereby, there remains a natural tendency for the attitude of the appendage to be corrected.
A yet further advantage of the device is that it allows a user to exercise the deficient appendage while its attitude is being corrected, and this is widely believed to be of great physiotherapeutic benefit.
Specific embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: